Production of microcapsules by simple coacervation

ABSTRACT

A microcapsule containing hydrous composition containing an electrolyte and microcapsules coated with a water-soluble polymer which undergoes phase separation by the action of the electrolyte. The electrolyte causes the above-mentioned phase separation comprising 5% to 80% by weight of water and water-soluble components.

BACKGROUND OF THE INVENTION

This is a continuation, of application Ser. No. 859,590 filed May 5,1986now U.S. Pat. No. 4,777,089.

1. Field of the Invention

The present invention relates to a hydrous composition containingmicrocapsules and a process for the production of microcapsules. Morespecifically, it relates to a hydrous composition containingmicrocapsules, in which useful components are protected stably bymicroencapsulation and the effect of the useful components can beexhibited by dissolution of the microcapsules when diluted with waterduring use.

2. Description of the Related Art

Methods for stably protecting useful components by microencapsulation inaqueous compositions are described in, for example, Japanese UnexaminedPatent Publication (Kokai) No. 49-453, Japanese Patent Publication(Kokoku) No. 50-25011, German Pat. No. 1,268,316, U.S. Pat. No.4,115,316. According to these methods, useful components are coated witha water-insoluble coating agent or useful components are coated with awater-soluble coating agent followed by application of chemicaltreatment on the coating agent for insolubilization to obtainwater-insoluble microcapsules, before being formulated into a hydrouscomposition. However, when this composition is used, it is necessary todestroy the microcapsules by the application of a mechanical force,whereby there is involved the problem that not only a long time isrequired before destruction of the microcapsules, but also the usefulcomponents cannot be utilized 100% effectively due to the difficulty indestroying uniformly all of the microcapsules. Further, since amechanical force is required during use, the scope of usage has beenitself limited.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No.50-3105 proposes to formulate water-soluble microcapsules in ananhydrous shampoo or rinse composition. However, since the compositionis made anhydrous, there are problems such that useful water-solublecomponents become insolubilized to make formulation difficult or thatthe price of the composition becomes higher, and its uses have been alsolimited.

Microcapsules have excellent functions such that liquid or gaseousmaterials can be handled as solid materials, that substances readilyreactive with each other can be separated, that substances can beprotected from the surrounding enviroment, and that the conditions forreleasing the core material can be controlled. Various processes havebeen known for the preparation of such microcapsules. Among them, theprocess for production of microcapsules by utilization of liquid-liquidphase separation (coacervation) is an industrially useful productionprocess, since excellent microcapsules having a high coating ratio anddense coating can be produced with a high efficiency.

However, in the prior art, when attempts are made to producemicrocapsules with a wall material of a polyvinyl alcohol according tothis process, a useful microcapsule cannot be obtained, because of thedifficulty in forming the separated phase endowed with the physicalproperties demanded for capsule formation. For example, whenmicrocapsules are produced according to the simple coacervation methodby the addition of an electrolyte to an equeous polyvinyl alcoholsolution, the separated phase fails to enclose the capsule core materialor, if the capsules are formed, the capsules became agglomerated into acoarse mass.

Under such circumstances, Japanese Examined Patent Publication (Kokoku)No. 47-51714 proposed a process for microencapsulation according to thesimple coacervation method with the use of a complicated bound productof a polyvinyl alcohol and a polyhydroxy aromatic substance as the wallmaterial. However, the polyhydroxy aromatic substance has a reducingability and exhibits strong chemical activity. The substance readilybinds or reacts with a metal or compounds having an amino, hydroxyl,aldehyde group, functionalities and therefore the core material may beundesirably denatured or deteriorated depending on the capsule corematerial employed. Also, the presence of a polyhydroxy aromaticsubstance discolored capsules in the presence of light, or metal ions.Japanese Examined Patent Publication (Kokoku) Nos. 47-51712 and 47-51713also teach the use of alkyleneglycol cyclic borates instead of thepolyhydroxy aromatic substance mentioned above. However, these additiveshave the same problems mentioned above.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to eliminate theabove-mentioned disadvantages of the prior art and to provide acomposition which can maintain stably useful components in an aqueouscomposition by microencapsulation and can release the useful componentsby dissolution of the microcapsules when diluted with water during use.

Another object of the present invention is to produce microcapsules witha polyvinyl alcohol as the wall material efficiently by a simpleprocedure.

Other objects and advantages of the present invention will be apparentfrom the following description.

In accordance with the present invention, there is provided amicrocapsule containing hydrous composition comprising (i) anelectrolyte and (ii) microcapsules composed of a core material coatedwith a water-soluble polymer which undergoes phase separation by theaction of said electrolyte. The content of the electrolyte is 5% to 80%by weight based on the total weight of water and the electrolyte.

In accordance with the present invention, there is also provided aprocess for producing microcapsules according to the simple coacervationmethod by dispersing a capsule core material substantially insoluble inwater in an aqueous solution containing a first water-soluble polymerselected from the group consisting of polyvinyl alcohol, sulfatedcellulose, water-soluble nylon, gelatin, and poly(meth)acrylic acid andalso adding the inorganic or organic salt thereto, which comprisesincorporating a second water-soluble polymer which undergoessubstantially no phase separation with the above inorgaic or organicsalt together with the first water-soluble polymer in said aqueoussolution.

From a study of the effect of electrolytes on the stability ofmicrocapsules, it has been found that microcapsules coated with awater-soluble polymer which undergoes phase separation with anelectrolyte penetrability of the film will be markedly improved andextremely stabilized when the electrolyte concentration reaches acertain level or higher, while they can be dissolved when diluted withwater. During dilution, it is possible to utilize the water contained insaliva, sweat, etc.

Also, ionic surfactants have been found to have similar functions aselectrolytes in general. Further, it has been discovered that somewater-soluble polymers which undergo substantially no phase separationwith inorganic electrolytes conventionally used may undergo specificphase separation with an ionic surfactant and become stabilized at acertain level of ionic surfactant or higher.

The electrolyte used in the present invention is contained in thecomposition in an amount of 5% to 80% by weight. The electrolyte isadded in an amount which makes the microcapsules coated with thewater-soluble polymer substantially inpenetrable, and it is formulatedto be contained in an amount within the range from 5% to 80% by weightbased on the total weight of the water and the electrolyte. Theelectrolyte concentration at which inpenetrability of the film ismarkedly improved differs depending on the electrolyte within the rangefrom 5% to 80%. For example, it is about 5% in the case of sodiumsulfate, and about 10% in the case of sodium chloride. A preferableconcentration of the electrolyte is 10 to 60% by weight. If theconcentration of the electrolyte is less than 5 weight %, the coatedfilm is very soft with a high water content and the microcapsules willbe markedly agglomerated. On the other hand, if the electrolyteconcentration is, too high solid electrolytes will precipitate, therebycausing undesirably separation of the system. Here, the electrolyteconcentration refers to the concentration of and electrolyte capable ofcontributing to phase separation of the water-soluble polymer.

As the electrolyte, there may be employed inorganic and organic salts,ionic surfactants, and amino acids, preferably having a high degree ofelectrolytic dissociation and high charges.

Inorganic salts may include, for example, water-soluble metal salts andammonium salts of inorganic acids such as sulfuric acid, sulfurous acid,hydrochloric acid, perchloric acid, hypochloric acid, phosphoric acid,metaphosphoric acid, boric acid, iodic acid, periodic acid, carbonicacid, vanadic acid, tungstic acid, silicic acid, nitric acid, nitrousacid, hydrofluoric acid, hydrobromic acid, etc.

Organic salts may include, for example, water-soluble metal salts andammonium salts of organic acids, amino acids and water-soluble metalsalts thereof, chelating agents, quaternary ammonium salts, and others.

Amino acids may include, for example, glutamic acid, alanic acid,glycine, and asparginic acid.

Among the electrolytes, ionic surfactants may be included. Ionicsurfactants can cause phase separation even for water-soluble polymerswhich will not undergo phase separation with conventional electrolytessuch as inorganic electrolytes. Examples of ionic surfactants are shownbelow.

Anionic Surfactants:

Carboxylic acid salts such as soap, N-acylamino acid salts,alkylethercarboxylic acid salts, acylated peptides, etc.

Sulfonic acid salts such as alkylsulfonic acid salts, alkylbenzene oralkylnaphthalenesulfonic acid salts, sulfosuccinic acid salts,α-olefinsulfonic acid salts, N-acylsulfonic acid salts,alkylamidosulfonic acid salts, α-sulfoaliphatic acid ester, etc.

Sulfate salts such as sulfated oils, alkyl sulfate salts, alkylethersulfate salts, alklarylether sulfate salts, alkylamide sulfate salts,etc.

Phosphate ester salts such as alkyl phosphate salts, alklether phosphatesalts, alkylarylether phosphates, etc.

Amphoteric Surfactants:

Alkylbetaine type amphoteric surfactants such as alkylcarboxybetainetype, alkylsulfobetaine type; alkylaminocarboxylic acid salts;imidazoline derivative type amphoteric surfactants such asalkylimidazoliniumbetaine type, etc., and phosphate type amphotericsurfactants.

Cationic Surfactants:

Fatty acid amine salts and quaternary ammonium salts.

Aromatic quaternary ammonium salts.

Heterocyclic quaternary ammonium salts such as alkylpyridinium salts,alkylimidazolium salts, etc.

The water-soluble polymers to be used in the present invention thosewhich can undergo phase separation into two phases of a highlyconcentrated phase and a low concentrated phase of polymers by theaddition of an electrolyte, preferably a polymer of which the highlyconcentrated phase becomes further intensified by increasing theconcentration of the electrolyte.

Examples of the water-soluble polymer which can undergo phase separationwith conventional electrolytes, such as inorganic salts, and ionicsurfactants include, for example, polyvinyl alcohol, sulfated cellulose,casein alkali metal salts, water-soluble nylons, and methyl cellulose.

The polyvinyl alcohol usable in the present invention comprises at least50% by weight of vinyl alcohol components in the polymer. In addition tothe polymer (homopolymer) in which all the polymers consist of vinylalcohol units, polymers with 50% by weight or more of vinyl alcoholcomponent and which contain other components such as vinyl acetate,vinyl propionate, vinyl butyrate, etc., and anionically modifed productsthereof, or cationically modified products thereof are also included inthe polyvinyl alcohol as mentioned in the present invention.

Polyvinyl alcohols are generally available as hydrolyzates of polyvinylacetates, having preferably 70 to 100 mole % of hydrolysis. Also, two ormore polyvinyl alcohols with different hydrolysis ratios may be used asa mixture. The concentration of the polyvinyl alcohol in an aqueoussolution suitably should be 0.5 to 15% by weight, preferably 1 to 10% byweight.

Water-soluble nylons are modified polyamides endowed with the functionof being soluble in water or alcohols as exemplified by a commercialproduct of AQ nylon produced by Toray K. K.

Water-soluble polymers capable of causing phase separation with ionicsurfactants include carboxymethyl cellulose, hydroxyethyl cellulose,hydroxypropyl cellulose, hydroxypropylmethyl cellulose, gum arabic,carageenan, arginic acid salts, guar gum, phosphorylated guar gum,pectin, xanthan gum, furcellaran, arabinogalactan, carboxymethyl orethyleneglycol derivatives of chitin or chitosan, gum karaya, spino gum,gum tragacanth, locust bean gum, tamarind gum, hydrolyzed ethylenemaleic anhydride copolymer, hydrolyzed methyl vinyl ether-maleicanhydride copolymer, and poly(meth)acrylic acid salts.

Water-soluble polymers capable of causing phase separation withinorganic or organic salts or amino acids are gelatine andpoly(meth)acrylic acid. Examples of gelatin may include alkali methodgelatin and acidic treated gelatin.

The composition of the present invention can be produced by applying theprocess for producing microcapsules in general. For example, when theuseful material (core material) is hydrophobic, microcapsules can beproduced according to the coacervation method in general in which theuseful material is dispersed in fine particles in an aqueous solution ofa water-soluble polymer, and a non-solvent for the polymer or anelectrolyte is added, or a pH change is effected. In the case when thewater-soluble polymer is a polyvinyl alcohol, it is preferable to usethe process proposed by the present applicant under the title of"Process for Production of Microcapsules" filed in Japan as JapanesePatent Application No. 60-95978 on May 8, 1985, and published asJapanese unexamined patent publication Kokai No. JP-A-61-254,243 onNovember 12, 1986. This process permits a water-soluble polymer whichdoes not undergo phase separation with the added electrolytes to beco-present in the aqueous solution in effecting phase separation of anaqueous polyvinyl alcohol solution with an electrolyte, whereby nocoarse agglomeration of microcapsules occurs but stable microcapsulescan be obtained. It is also possible to utilize the orifice process inwhich a double nozzle is used, the spray drying process, the pan coatingprocess, etc.

When the useful component is a hydrophilic material, microcapsules canbe produced by spraying a coating solution on the surface of the usefulmaterial (core material) according to the pan coating process, fluidizedbed coating process, etc. Also, the spray drying process is utilizable.On the other hand, when the useful material is a liquid, themicrocapsules can be prepared according to the processes as mentionedabove after it is absorbed or adsorbed onto fine powder or adsorbents.The microcapsule obtained is dispersed in an aqueous liquid compositionso that the electrolyte concentration may be 5% to 80% by weight. It isalso possible to prepare a composition in the form of a slurry of pasteby dispersing water-insoluble particles in a composition.

According to the present invention, as mentioned above, microcapsulescan be prepared according to a simple coacervation method by dispersinga capsule core material substantially insoluble in water in an aqueoussolution containing a first water-soluble polymer selected from thegroup consisting of polyvinyl alcohol, sulfated cellulose, water-solublenylon, gelatin, and poly(meth)acrylic acid and also adding inorganic ororganic salt thereto, which comprises incorporating a secondwater-soluble polymer which undergoes substantially no phase separationwith the above inorganic or organic salt together with the firstwater-soluble polymer in said aqueous solution. Examples of the secondwater-soluble polymer which undergoes substantially no phase separationwith an electrolyte include carboxymethyl cellulose, methyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethylcellulose, polyvinyl pyrrolidone, polyacrylic acid salts,hydroxypropylated starch, alginic acid salts, carageenan, gum arabic,xanthan gum, pectin, furcellaran, guar gum, gum karaya, spino gum, gumtragacanth, locust bean gum, tamarind gum, hydrolyzed ethylene-maleicanhydride copolymer, hydrolyzed methyl vinyl ether-maleic anhydridecopolymer, and poly(meth)acrylic acid salts. Among them, carboxymethylcellulose, hydroxypropylated starch, and alginic acid salts pectin,furcellaran, guar gum, gum karaya, spinio gum, gum tragacanth, locustbean gum, tamarind gum, hydrolyzed ethylene-maleic anhydride copolymer,hydrolyzed methyl vinyl ether-maleic anhydride copolymer, andpoly(meth)acrylic acid salts are preferred. Especially when pectin isused in combination with furcellaran, guar gum, gum karaya, spino gum,gum tragacanth, locust bean gum, or tamarind gum, microcapsules having athicker wall can be advantageously obtained without causing theagglomeration of the resultant microcapsules.

The second water-soluble polymer which undergoes substantially no phaseseparation with an electrolyte (hereinafter called water-solublepolymer) should be contained in the aqueous solution suitably at aconcentration of 0.005% to 20% by weight, preferably 0.01% to 10% byweight, and more preferably 0.1% to 10% by weight. The amount of thesecond water-soluble polymer added to the first water-soluble polymer inthe aqueous solution may be suitably 0.05 to 5 parts by weight,preferably 0.1 to 3 parts by weight of the second water-soluble polymer,per 1 part by weight of the first water-soluble polymer.

For the capsule core material, a solid or liquid material insoluble inwater is used as desired, depending on the purpose of use.

For the electrolyte, the above-mentioned inorganic and organic salts ingeneral may be used either alone or as a mixture of two or morecompounds.

Of these salts, it is preferable to use sulfates such as sodium sulfate,potassium sulfate, magnesium sulfate, aluminum sulfate, ammonium sulfateand the like; chlorides such as sodium chloride, potassium chloride,magnesium chloride, calcium chloride, ammonium chloride and the like;phosphates such as dipotassium hydrogen phosphate, potassium dihydrogenphosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate andthe like; carbonates such as sodium carbonate, sodium hydrogencarbonate, potassium hydrogen carbonate and the like.

In the present invention, a capsule core material is dispersed in anaqueous solution containing a first water-soluble polymer and a secondwater-soluble polymer which undergoes substantially no phase separationwith the above-mentioned salt, and also the salt is added thereto. Afterdispersion of the capsule core material in the aqueous solution, thesalt can be added to the dispersion system, or alternatively the saltcan be added before dispersion of the capsule core material.

The salt preferably should be added as an aqueous solution with aconcentration of 5% to 60% by weight. The amount of the salt added maybe preferably within a range which will give 2.0 to 20% by weight of thesalt concentration after addition.

Addition of the salt causes phase separation, whereby the aqueoussolution of the first water-soluble polymer appears as the separatedphase enclosing the capsule core material. The phase separation shouldbe carried out appropriately at a temperature of 10° to 80° C.

After completion of the phase separation, the capsule wall films aregelled by cooling to a temperature of about 0° C. to 10° C.

The capsules obtained are concentrated by centrifugation or other means,followed further by drying to be utilized as the capsules soluble inwater, or the wall films may be hardened to give capsules utilizable aswater-insoluble capsules. As the hardening method, there may beemployed, for example, the method in which hardening agents such asborax, water-soluble salts of vanadium or uranium, aldehydes, etc. areemployed.

The capsule particle size is determined substantially by the size of thecapsule core material and, for example, capsules with diameters of about1 to 5000 μm can be obtained.

The wall thickness of the microcapsules can also be controlled by addingsilica or a fatty acid metal salt substantially insoluble in water to anaqueous solution containing the first and second water-soluble polymer,or a capsule core material or both thereof. By addition of thesecontrolling agents, the thickness of the wall film of the capsule can bemade thicker. Since the thickness of the capsule wall film is madethicker by increasing the amount of the controlling agent added, thewall thickness can be controlled by the amount of the controlling agentadded.

As the silica, crystalline, amorphous, glassy or colloidal silicon oxidemay be available, preferably those commercially available as amorphoushydrous silica.

The fatty acid metal salt which is substantially insoluble in water mayinclude metal salts of fatty acids such as of calcium, magnesium,aluminum, iron, manganese, cobalt, lead, chromium, copper, zinc, nickel,etc., preferably metal salts of C₈ -C₂₂ fatty acids.

The composition of the present invention can be formulated into variousmicrocapsule-containing compositions by adding suitable activecomponents or additive components depending on the uses. The followingTable 1 shows application examples and examples of useful components(i.e., core materials) therein.

                  TABLE 1                                                         ______________________________________                                        Applied Articles and Components                                               Field        Article     Useful components                                    ______________________________________                                                         Detergent for                                                                             Perfume, bleaching                                                laundering  agent, enzyme,                                                                finishing agent for                                                           clothing                                         Diluted Washing  Detergent for                                                                             Perfume, Bleaching                               with    agent    kitchen (table-                                                                           agent, enzyme,                                   water,           ware)       hand roughening pre-                             capsules                     ventive                                          dissolved        Shampoo, Rinse                                                                            Perfume, Bleaching                               by addi-                     agent, conditioning                              tion of                      agent, sterilizer,                               water                        galenical                                                         Detergent for                                                                             Perfume, enzyme, steri-                                           face washing,                                                                             lizer, galenical                                                  hand washing,                                                                 bath                                                                          Detergent for                                                                             Perfume, enzyme, acid,                                            bathtub, toilet,                                                                          alkali, sterilizer, deodor-                                       glass, house                                                                              ant, water repellent                                              detergent for                                                                             Perfume, anti-rust agent                                          automobile                                                                    Bleaching agent                                                                           Bleaching agent, acti-                                                        vator perfume                                            Others   Volatilizer Perfume, volatilizer                                              Agent for bath                                                                            Perfume, galenical                                                Hair        Perfume, sterilizer,                                              conditioner galenical                                        Capsules                                                                              Oral     Tooth paste Flavor, enzyme, various                          dissolved                                                                             articles Tooth wash  pharmaceutical com-                              with water       Mouth washing                                                                             ponents (prevention of                           or saliva        agent       decayed teeth, preven-                           or sweat         Oral cream  tion of pyorrhea, re-                                                         moval of mouth odor,                                                          scaling), galenical                                               Washing agent                                                                             Enzyme, bleaching                                                 for artificial                                                                            agent, perfume                                                    teeth                                                                Cosme-   Anti-sweat  Perfume, sterilizer, anti-                               tics     agent       sweat agent                                                       Cream lotion                                                                              Perfume, pharmaceutical                                                       component, galenical,                                                         vitamin                                                  Foods    Dressing,   Flavor, condiment,                                                mayonnaise, vitamin, animal and ve-                                           mustard, wasabi,                                                                          getable oil                                                       purin, jelly                                                 ______________________________________                                    

According to the present invention, microcapsules coated in awater-soluble polymer can be stably maintained in a hydrous compositionduring storage, while the coated film can be rapidly dissolved only bydilution with water without requiring external forces to release usefulcomponents during usage.

Furthermore, according to the present invention, by giving rise to aliquid-liquid phase separation by the addition of an inorganic ororganic salt to an aqueous solution containing the above-mentioned firstand second water-soluble polymer molecules, a separated phase suitablefor capsule formation is formed to give good microcapsules with the wallfilm of the first water-soluble polymer.

EXAMPLE

The present invention will now be further illustrated by, but is by nomeans limited to, the following Examples.

Example 1

A condiment component (controlled to 2 to 20 μm of particle size by agrinding machine) obtained by extraction with ethyl alcohol from apurified oil residue of Rose Marie, which is a plant of the perillafamily, was used as the useful component. It has been previouslyproposed by the present Application in Japanese Unexamined PatentPublication (Kokai) No. 57-203,445 that this condiment component is acomponent having the effect of inhibiting (deodorizing) mouth odor. Byuse of this condiment component as the core material, microencapsulationwas conducted by applying the invention filed by the present applicantunder the title of "Process for Production of Microcapsules" in Japan asJapanese Patent Application No. 60-95978 on May 8, 1985, and publishedas Japanese unexamined patent publication Kokai No. JP-A-61-254,243 onNovember 12, 1986.

In 250 g of an aqueous solution containing 4% by weight of a polyvinylalcohol (saponification degree 86 to 89 mol %, polymerization degree500) and 4% by weight of a sodium carboxymethyl cellulose (CMC: 1%aqueous solution, viscosity 10 c.p.), 10 g of the condiment componentwas dispersed by means of a commercially available stirring machine. CMCis a water-soluble polymer which is permitted to coexist in the systemand it does not undergo phase separation by addition of sodium chloride.

Subsequently, 50 g of a 25% by weight of sodium chloride solution wasadded gradually at a temperature of 40° C. to obtain microcapsulescontaining the condiment component with the polyvinyl alcohol (particlesize 5 to 50 μm). Then, 62 g of sodium chloride, 0.5 g of sodium laurylsulfate and 1.5 g of a perfume were added and the mixture was cooled to10° C. After aging for 2 hours, the mixture was returned to roomtemperature to obtain a microcapsule containing hydrous composition.

The microcapsule containing hydrous composition was found to contain 20%by weight of electrolytes (sodium chloride and ionic surfactants) and,when it was diluted to 50-fold or more with water, it was confirmed thatthe polyvinyl alcohol coated film of the microcapsules was dissolved inwater to disappear by observation with an optical microscope. Themicrocapsule containing hydrous composition can be used as the mouthwashing agent having mouth deodorizing action. Regarding stabilizationof the condiment component by microencapsulation, a description is givenin the following Comparative Example 1.

Comparative Example 1

In Example 1, no polyvinyl alcohol was used but instead water was usedto prepare a composition containing the condiment component not coatedwith the polyvinyl alcohol.

For the compositions of Example 1 and Comparative Example 1, stabilityof each condiment component was tested according to the accelerationtest (stored at 40° C. for 30 days). After storage, the sample wasdiluted to 100-fold with water and 500 ng of methylmercaptan waspermitted to act on 3 mg of the condiment component. The percentage ofmethylmercaptan captured was measured by gas chormatography to determinethe deodorant activity (%). The results are shown in Table 2. From Table2, it can be seen that a condiment component coated with the polyvinylalcohol of Example 1 is clearly more stable than Comparative Example 1.

                  TABLE 2                                                         ______________________________________                                                       Days of storage                                                Sample           0          15    30                                          ______________________________________                                        Example 1        100        95    90                                          Comparative Example 1                                                                          100        30    10                                          ______________________________________                                    

Comparative Example 2

Example 1 was repeated except that 62 g of sodium chloride was not addedafter preparation of the microcapsules. In this case, the concentrationof the electrolytes (sodium chloride+ionic surfactant) was 4.17% byweight. When this composition was stored at 40° C., microcapsules becameagglomerated one day afterwards to form coarse masses.

Example 2

A condiment composition was prepared, comprising 50% by weight of acondiment component obtained by extraction with n-hexane from thepurified oil residue of Rose Marie, which is a plant of the perillafamily, and 50% by weight of rapeseed oil. This condiment component is acomponent having the effect of inhibiting (deodorizing) mouth odor.

In 250 g of an aqueous solution containing 4% by weight of a polyvinylalcohol (saponification degree 86 to 89 mol %, polymerization degree500) and 4% by weight of sodium carboxymethyl cellulose (CMC: 1% aqueoussolution, viscosity 10 c.p.), 10 g of the condiment composition wasemulsified at 70° C. by means of a commercially available emulsifyingmachine to prepare a dispersion of the condiment composition withparticle sizes of 20 to 80 μm. CMC has the same function as in Example1.

Next, to the dispersion was gradually added at 40° C. an aqueous 25% byweight of sodium chloride to obtain microcapsules containing thecondiment composition coated with the polyvinyl alcohol (particle size30 to 100 μm). Subsequently, after 62 g of sodium chloride was added tothe microcapsules, the mixture was cooled to 10° C. and aged thereat for2 hours and then returned to room temperature. Then, according tocentrifugal separation, a microcapsule dispersion containing 30% byweight of microcapsules containing the condiment composition coated witha polyvinyl alcohol and 14.8% by weight of sodium chloride. To 5 g ofthe microcapsule dispersion, the following components were added toprepare a microcapsule containing hydrous composition.

    ______________________________________                                        Calcium carbonate       40 g                                                  Solvitol                20 g                                                  Carboxymethyl cellulose 1.0 g                                                 Sodium lauryl sulfate   2.0 g                                                 Sodium saccharide       0.02 g                                                Perfume                 0.5 g                                                 Sodium chloride         10 g                                                  Water                   21.48 g                                               ______________________________________                                    

This microcapsule containing hydrous composition contain 21.8% by weightof electrolytes inclusive of ionic surfactants on the basis of the wholeweight from which water-insoluble components are removed as being 100,and it is useful as tooth paste having a mouth deodorizing action. Toothpolishing was performed with said microcapsule containing hydrouscomposition and thereafter the liquid in the mouth was taken out foroptical microscopic observation. As the result, the microcapsule coatingwas found to be dissolved. Thus, it was found that the microcapsuleswere not dissolved in the microcapsule containing hydrous composition,but dissolved with a small amount of water and saliva. Regardingstabilization of the condiment component by microencapsulation, this isdescribed in Comparative Example 3 shown below.

Comparative Example 3

In Example 2, polyvinyl alcohol was not used but instead water was usedto prepare a composition containing the condiment composition not coatedwith the polyvinyl alcohol. For the composition of Example 2 andComparative Example 3, stability of the condiment component was testedby the acceleration test (stored at 40° C. for 30 days) to determine thedeodorant activity (%) similarly as Example 1, and the results are shownin Table 3. From Table 3, it can be seen that the condiment componentcoated with the polyvinyl alcohol is clearly more stable than that ofComparative Example 3.

                  TABLE 3                                                         ______________________________________                                                       Days of storage                                                Sample           0          15    30                                          ______________________________________                                        Example 2        100        93    90                                          Comparative Example 3                                                                          100        20    10                                          ______________________________________                                    

Example 3

In 250 g of an aqueous solution containing 4% by weight of a polyvinylalcohol (saponification degree 86 to 89 mol %, polymerization degree500) and 4% by weight of a carboxymethyl cellulose (CMC: 1% aqueoussolution, viscosity 10 c.p.), 3 g of silica powder (white carbon) wasdispersed and then 20 g of a perfume composition (fruit type perfume 5%,olive oil 95%) was emulsified in a stirring tank to particle sizes of200 to 500 μm. The function of CMC is the same as in Example 1.

Subsequently, 50 g of a 25% aqueous sodium chloride was gradually addedat 40° C. to obtain microcapsules containing the perfume compositionwith the polyvinyl alcohol (particle size 200 to 600 μm). After theaddition of 60 g of sodium chloride to the microcapsules, the mixturewas cooled to 5° C. and then left to stand at room temperature. Themicrocapsule phase of the upper phase was separated to obtain amicrocapsule dispersion containing 30% by weight of microcapsules and14.5% by weight of sodium chloride. To 3 g of the thus preparedmicrocapsule dispersion, the following components were added to preparea microcapsule containing hydrous composition.

    ______________________________________                                        Sodium polyoxyethylene alkyl ether sulfate                                                               15 g                                               Sodium lauryl sulfate      7 g                                                Anhydrous sodium sulfate   3 g                                                Perfume                    0.5 g                                              Water                      71.5 g                                             ______________________________________                                    

In these compositions, the total concentration of the electrolytesinclusive of ionic surfactants is 25.4% by weight. The above compositionis useful as shampoo. When this composition was stored at 40° C. for 30days, the microcapsules were stable without being destroyed. When hairwas washed with this composition (shampoo), the microcapsules wereimmediately dissolved by the spraying of water to generate the perfumefragrance of the contents.

Example 4

To 5 g of the microcapsule dispersion prepared according to theprocedure of Example 3 (containing 30% by weight of microcapsules,containing fruit type perfume composition coated with the polyvinylalcohol, and 14.5% by weight of sodium chloride), the followingcomponents were added to prepare a microcapsule containing hydrouscomposition containing 30.7% by weight of electrolytes.

    ______________________________________                                        Sodium α-olefinsulfonate                                                                        22 g                                                  Straight magnesium      6 g                                                   alkylbenzenesulfonate                                                         Anhydrous sodium sulfate                                                                              2 g                                                   Ethyl alcohol           3 g                                                   Perfume                 0.5 g                                                 Water                   61.5 g                                                ______________________________________                                    

This microcapsule containing hydrous composition is useful as adetergent for tableware. The microcapsules are stable in thiscomposition without destruction or dissolution, and remain stable evenafter elapse of 30 days at 40° C. When used in a standard use amount ofthe detergent for tableware (1.5 ml dissolved in one liter of water),the microcapsules were dissolved in water to generate a fresh fruit typefragrance.

Example 5

To 5 g of microcapsules containing 10% by weight of a perfume as thecore material coated with carboxymethyl cellulose prepared by the spraydrying method (particle size to 100 to 500 μm), the following componentswere added to prepare a microcapsule containing composition containing39% by weight of ionic surfactant.

    ______________________________________                                        Sodium straight alkyl sulfate                                                                          25 g                                                 Sodium α-olefinsulfonate                                                                         5 g                                                  Sodium toluenesulfonic acid                                                                            7 g                                                  Sodium hydroxide         4 g                                                  Glycine                  8 g                                                  Perfume                  0.1 g                                                Water                    45 g                                                 ______________________________________                                    

This composition is useful as a detergent for clothing. Themicrocapsules in this composition are stable without destruction ordissolution, and when it was used in a standard use amount (20 g ofcomposition added to 30 liters of water), the capsules were dissolved inwater to generate a strong smell of perfume.

Example 6

A 500 g amount of an aqueous solution containing 5% by weight of apolyvinyl alcohol (saponification degree: 87 to 89 mole %;polymerization degree: 500) and 5% by weight of a carboxymethylcellulose (etheration degree: about 0.6; polymerization degree: 100 to150) and 25 g of an olive oil (core material) were charged in aone-liter stirring tank, and the olive oil was dispersed by stirring tocontrol its particle sizes to 50 to 150 μm.

Subsequently, 250 g of an aqueous 25% sodium chloride solution wasgradually added at a temperature of 40° C. Liquid-liquid phaseseparation of the polyvinyl alcohol solution occurred by addition of theaqueous sodium chloride solution, and the separated phase enclosed thedispersed olive oil particles to form capsules with liquid walls.

For firming the film by a reduction of the water content in the capsulefilms, 90 g of sodium chloride was further added, followed by cooling to20° C. The thickness of the wall film of the capsule thus obtained wasmeasured by observation with an optical microscope. The results aredescribed hereinafter together with those of Examples 2 to 5. Thecapsules can be separated from the aqueous solution and dried for use,but the capsule walls were chemically hardened by stirring for 15 hourswith the addition of 20 ml of an aqueous 50% by weight glutaraldehydesolution.

Example 7

The same procedure as Example 6 was conducted except for adding 7.5 g ofan amorphous hydrous silica to the aqueous solution containing thepolyvinyl alcohol and the carboxymethyl cellulose (aqueous phase).

Example 8

The same procedure as Example 6 was conducted except for adding 25 g ofan amorphous hydrous silica to the aqueous solution containing thepolyvinyl alcohol and the carboxymethyl cellulose (aqueous phase).

Example 9

The same procedure as Example 6 was conducted except for adding 2.5 g ofan amorphous hydrous silica to the olive oil (core material).

Example 10

The same procedure as Example 6 was conducted except for adding 2.5 g ofcalcium stearate (fine powder) to the olive oil (core material).

Example 11

The same procedure as Example 6 was conducted except for adding 2.5 g ofan amorphous hydrous silica to the aqueous solution containing polyvinylalcohol and carboxymethyl cellulose (aqueous phase) and also adding 2.5g of calcium stearate (fine powder) to the olive oil (core material).

The results of measurements of the capsules obtained in Examples 6 to 11after dehydration are shown in Table 1. As is apparent from Table 1, thethickness of the capsule wall film can be controlled by the addition ofsilica and/or calcium stearate to the aqueous phase and/or the corematerial.

                  TABLE 4                                                         ______________________________________                                                                    Thickness of                                      Example  Additive           capsule (μm)                                   ______________________________________                                        6        None               1                                                 7        Silica 7.5 g (in aqueous phase)                                                                  8                                                 8        Silica 25 g (in aqueous phase)                                                                   15                                                9        Silica 2.5 g (in core material)                                                                  3                                                 10       Calcium stearate 2.5 g (in core                                                                  2                                                          material)                                                            11       Calcium stearate 2.5 g (in core                                               material)                                                                     Silica 2.5 g (in aqueous phase)                                                                  5                                                 ______________________________________                                    

Comparative Example 4

Example 6 was repeated except that an aqueous solution containing onlypolyvinyl alcohol was used without the use of carboxymethyl cellulose.After 250 g of an aqueous 25% sodium chloride solution was graduallyadded, the liquid-liquid phase separation of the polyvinyl alcoholsolution occurred therewith to form a capsule. When 90 g of sodiumchloride was further added, coarse masses of the phase separatedproducts several millimeters to several centimeters in size were formed.

Example 12

An amount of 500 g of an aqueous solution containing 3% by weight of apolyvinyl alcohol (saponification degree: 87 to 89 mole %,polymerization degree: about 500) and 10% by weight of hydroxypropylatedstarch (Stacodex produced by Matsutani Kagaku Kogyo K.K.) and 85 g of aperfume composition (composition composed mainly of phenyl ethylalcohol, hexylsalicylate, α-hexylcinnamicaldehyde, etc.) were charged inone-liter stirring tank, and the perfume composition was dispersed bystirring to control its particle sizes to 30 to 100 μm. Subsequently,100 g of an aqueous 20% by weight of sodium sulfate solution was addedgradually at 40° C. By addition of the aqueous sodium sulfate solution,the liquid-liquid phase separation of the polyvinyl alcohol solutionoccurred, and the separated phase enclosed the dispersed particles(perfume composition particles) to form capsules with liquid wallshaving a wall thickness of 5 to 10 μm before dehydration (wall thicknessafter dehydration: 1 to 5 μm).

After cooling to 10° C., 20 ml of an aqueous 50% by weight ofglutaraldehyde solution was added and the mixture was stirred for 15hours, followed further by stirring at an elevated temperature of 40° C.for 3 hours to thereby chemically harden the capsule walls.

The capsules were separated by centrifugation, washed with water anddried. When the capsules were disintegrated, a perfume fragrance wasgenerated.

Example 13

An amount of 500 g of an aqueous solution containing 3.5% by weight of apolyvinyl alcohol (saponification degree: 87 to 89 mole %,polymerization degree: about 500), 1.5% by weight of a polyvinyl alcohol(saponification degree: 100%, polymerization degree: about 500) and 5%by weight of a carboxymethyl cellulose (etheration degree: 0.6,polymerization degree: 100 to 150) was charged in an one-liter stirringtank, and 5 g of an aqueous 10% sodium sulfate solution was graduallyadded under stirring. A small amount of the separated layer of polyvinylalcohol was thereby formed in droplets.

Subsequently, a core material having 6 g of an amorphous hydrous silicadispersed in 60 g of a fluid paraffin was added and further 95 g of anaqueous 20% sodium sulfate solution was gradually added. Stirring wascontrolled so that the particle sizes of the dispersed fluid paraffinbecame 50 to 200 μm. By addition of the aqueous sodium sulfate solution,polyvinyl alcohol enclosed the dispersed particles (fluid paraffinhaving silica dispersed therein) to form capsules. Subsequently, thecapsules were cooled to 5° C. and the wall films of the capsules werehardened with the addition of 5 g of borax. After separation bycentrifugation, the dried capsules were broken to release the fluidparaffin.

Example 14

An amount of 500 g of an aqueous solution containing 3% by weight of apolyvinyl alcohol (saponification degree: 87 to 89 mole %,polymerization degree: about 500) and 0.5% by weight of sodium alginateand 90 g of a silicone oil were charged in a one-liter stirring tank,and the silicone oil was dispersed by stirring to control its particlesized to 500 to 2000 μm. Subsequently, 250 g of an aqueous 25% by weightof sodium chloride solution was gradually added. By addition of thesodium chloride solution, the liquid-liquid phase separation of thepolyvinyl alcohol solution occurred, whereby substantially sphericalcapsules having liquid walls enclosing the dispersed particles wereformed. After the addition of 10 g of sodium chloride, the capsules werecooled to 5° C. and 5 g of borax was added to harden the wall films ofthe capsules. After drying, the capsules were broken to release thesilicone oil.

Example 15

A 400 g amount of an aqueous solution containing 5% by weight ofpolyvinyl alcohol (saponification degree: 87 to 89 mole %;polymerization degree: 500), 0.6% by weight of guar gum (available fromSanei Kagaku Kogyo Kabushiki Kaisha, Bistop LH-303), and 0.4% by weightof pectin (lemon) (available from Junsei Kagaku Kabushiki Kaisha, about60% galactoronic acid) and 40 g of an olive oil (i.e., core material)were charged in a one-liter stirring tank, and the olive oil wasdispersed by stirring to control its particle sizes to 800 to 1200 μm.

Subsequently, 250 g of an aqueous 25% sodium chloride solution wasgradually added at a temperature of 40° C. Liquid-liquid phaseseparation of the polyvinyl alcohol solution occurred by addition of theaqueous sodium chloride solution, and the separated phase enclosed thedispersed olive oil particles to form capsules with liquid walls.

For firming the film by a reduction of the water content in the capsulefilms, 75 g of sodium chloride was further added, followed by cooling to10° C., the resultant capsules may be used by separating from theaqueous solution, followed by drying. However, the resultant capsuleswere charged with 20 ml of a 50% by weight aqueous glutaraldehydesolution and the resultant mixture was warmed to 40° C. for 5 hourswhile stirring. Thus, the capsule walls were chemically hardened.

During all the steps, the desired substantially spherical capsuleshaving a thickness of the coated film of 40 to 80 μm were obtainedwithout causing agglomerat of the particle.

Comparative Example 6

The same procedure as Example 15 was conducted except that guar gum andpectine (i.e., lemon) was not formulated.

After gradually adding 250 g of an aqueous 25% sodium chloride solution,liquid-liquid phase separation of the polyvinyl alcohol solutionoccurred. However, the dispersed olive oil particles were not enclosedand no capsules were formed.

When 75 g of sodium chloride was added, the phase separated coarse masshaving a size of several millimeters to several centimeters was formed.

Comparative Example 7

The same procedure as Example 15 was conducted except that pectine(i.e., lemon) was not formulated.

When an aqueous 25% sodium chloride solution was gradually added,liquid-liquid phase separation of the polyvinyl alcohol solutionoccurred and the core material (i.e., an olive oil) was enclosedtherewith to form capsules with liquid walls. However, after adding anaqueous 25% sodium chloride solution, the capsules were agglomerated andthe agglomerated products were deposited on the agitation blades and thewalls of the vessel.

Example 16

A 400 g amount of an aqueous solution containing 5% by weight of gelatin(acid treatment method, isoelectric point=8.9), 1.0% by weight of guargum (available from Sanei Kagaku Kogyo Kabushiki Kaisha, Bistop LH-303),and 0.001% by weight of pectin (apple) (available from Sanei KagakuKogyo Kabushiki Kisha, Marpee NL) and 30 g of allylisothiocyanate (i.e.,allylated mustard oil, core material) were charged in a one-literstirring tank, and the allylisothiocyanate was dispersed by stirring tocontrol its particle sizes to 50 to 250 μm.

Subsequently, 400 g of an aqueous 30% sodium dihydrogenphosphatesolution was gradually added at a temperature of 40° C. Liquid-liquidphase separation of the gelatin solution occurred by addition of theaqueous sodium dihydrogenphosphate solution, and the separated phaseenclosed the dispersed allylisothiocyanate particles to form capsuleswith liquid walls.

For firming the film by a reduction of the water content in the capsulefilms, after cooling to 10° C., 170 g of sodium dihydrogenphosphate wasfurther added, followed by aging for 2 hours. Thus, the desiredmicrocapsules containing allylisothiocyanate therein and having aparticle size of 70 to 300 μm and a gelatin wall thickness of 10 to 40μm were obtained.

These capsules can be formulated into, as a capsule dispersion, foodssuch as paste mustard, paste horseradish, and dressings. Alternatively,afer separating and drying the capsules, the microcapsules can beformulated, as a spice, into various foods. When the resultantmicrocapsules were placed in an oral cavity, the wall membranes of thecapsules were dissolved and spicy taste came to the nose.

Comparative Example 8

The same procedure as Example 16 was conducted except that guar gum andpectine (i.e., apple) was not formulated.

After gradually adding 400 g of an aqueous 30% sodiumdihydrogenphosphate solution, liquid-liquid phase separation of thegelatin solution occurred. However, the core material were notsubstantially enclosed by the separated liquid particles and only a verysmall amount of the core material was nonuniformly enclosed with thephase separated liquid particles.

Subsequently, after cooling to 10° C., when sodium dihydrogenphosphatewas added, the capsules were deformed and most of them were destroyed.Thus, the allylisothiocyanate having a water solubility of 0.2% cannotbe sufficiently encapsulated by an ordinal method.

When 75 g of sodium chloride was added, the phase separated coarse masshaving a size of several millimeters to several centimetes was formed.

Comparative Example 9

The same procedure as Exmaple 16 was conducted except that pectine(i.e., apple) was not formulated.

When an aqueous 30% sodium dihydrogenphosphate solution was graduallyadded, liquid-liquid phase separation of the gelatin solution occurredand the core material (i.e., allylisothiocyanate) was enclosed therewithto form capsules with liquid walls. However, after gradually adding anaqueous 30% sodium dihydrogenphosphate solution, the capsules wereagglomerated and the agglomerted products were deposited on theagitation blades and the walls of the vessel.

Example 17

A 400 g amount of an aqueous solution containing 4% by weight of gelatin(acid treatment method, isoelectric point=8.9) polymerization degree:500), 0.8% by weight of guar gum (available from Dainihon SeiyakuKabushiki Kaisha, Guapack PN), and 0.01% by weight of pectin (apple)(available from Sanei Kagaku Kogyo Kabushiki Kaisha, Marpee OM) and 40 gof an orange oil (i.e., core material) were charged in a one-literstirring tank, and the orange oil was dispersed by stirring to controlits particle sizes to 50 to 150 μm.

Subsequently, 400 g of an aqueous 30% sodium citrate solution wasgradually added at a temperature of 40° C. Liquid-liquid phaseseparation of the gelatin solution occurred by addition of the aqueoussodium citrate solution, and the separated phase enclosed the dispersedorange oil particles to form capsules with liquid walls.

For firming the film by a reduction of the water content in the capsulefilms, 50 g of sodium citrate was further added, after cooling to 10°C., followed by aging for 2 hours. The resultant capsules were separatedand dried. The capsules thus obtained could be used as a food additive.

Example 18

A 500 g amount of an aqueous solution containing 3% by weight ofwater-soluble nylon (available from Toray Co. P-70), 0.2% by weight ofguar gum (available from Sanei Kagaku Kogyo Kabushiki Kaisha, BistopLH-303), and 0.005% by weight of pectin (apple) (available from SaneiKagaku Kogyo Kabushiki Kaisha) and 35 g of liquid paraffin (i.e., corematerial) were charged in a one-liter stirring tank, and the liquidparaffin was dispersed by stiring to control its particle sizes to 50 to200 μm.

Subsequently, 250 g of an aqueous 15% sodium sulfate solution wasgradually added at a temperature of 40° C. Liquid-liquid phaseseparation of the aqueous nylon solution occurred by addition of theaqueous sodium sulfate solution, and the separated phase enclosed thedispersed liquid paraffin particles to form capsules with liquid walls.

For firming the film by a reduction of the water content in the capsulefilms, 42 g of sodium sulfate was further added, after cooling to 20° C.Thus, the good microcapsules having a particle size of 60 to 220 μm anda wall thickness of 5 to 20 μm were obtained without causingagglomeration. Although the resultant capsules can be hardened with, forexample, an isocyanate compound, the capsules can be used in, forexample, cosmetics after separating and drying.

Comparative Example 10

The same procedure as Example 18 was conducted except that guar gum andpectine (i.e., lemon) was not formulated.

After gradually adding 250 g of an aqueous 25% sodium sulfate solution,liquid-liquid phase separation of the water-soluble nylon solutionoccurred and the dispersed liquid paraffin particles were encapsuled.However, when 42 g of sodium sulfate was added after cooling to 20° C.,the capsules were remarkably agglomerated and the agglomerated productswere deposited on the agitation blades.

We claim:
 1. A process for producing microcapsules according to a simplecoacervation method by dispersing a capsule core material substantiallyinsoluble in water in an aqueous solution containing a firstwater-soluble polymer selected from the group consisting of polyvinylalcohol, sulfated cellulose, water-soluble nylon, gelatin, andpoly(meth)acrylic acid and also adding inorganic or organic saltthereto, which comprises incorporating a second water-soluble polymerwhich undergoes substantially no phase separation with the aboveinorganic or organic salt together with the first water-soluble polymerin said aqueous solution, the concentration of the second water-solublepolymer in the aqueous solution being 0.1% to 10% by weight and theamount of the weight ratio of second water-soluble polymer added to thefirst water-soluble polymer in the aqueous solution is 0.05 to 5 partsby weight, per 1 part by weight of the first water-soluble polymer.
 2. Aprocess as claimed in claim 1, wherein said second water-soluble polymeris selected from the group consisting of carboxymethyl cellulose,hydroxypropylated starch, alginic acid salts, pectin, guar gum, gumkaraya, spino gum, gum tragacanth, locust bean gum, tamarind gum,hydrolyzed ethylene-maleic anhydride copolymer, hydrolyzed methyl vinylether-maleic anhydride copolymer, and poly(meth)acrylic acid salts andmixtures thereof.
 3. A process as claimed in claim 1, wherein saidsecond water-soluble polymer is a mixture of pectin with guar gum, gumkaraya, spino gum, gum tragacanth, locust bean gum, or tamarind gum.